Blanch the tomatoes in boiling water for 1 minute. Drain and slip off the skins. Remove the seeds, chop coarsely, and let drain.
Mix the ricotta and egg yolks in a large bowl until smooth. Add the tomatoes, parsley, nutmeg, salt, and pepper, and mix well. Form the mixture into croquettes of about 2 inches long and 1 inch thick. The mixture should be firm; if it is too runny, add 1-2 tablespoons dry bread crumbs or freshley grated Parmesan cheese.
Dredge the croquettes in the flour, dip them in the egg, and roll in the bread crumbs.
Heat the oil in a large frying pan until very hot. Fry the croquettes in small batches until golden brown, about 10 minutes.
Remove with a slotted spoon and drain well. Serve hot.